Almost all the heads of golf clubs and putters sold today have a geometrically unsymmetrical shape and/or are affixed in an offset relationship to the longitudinal center of their respective club shafts. In order to accurately hit a golf ball and obtain a maximum distance of flight, it is necessary to address the ball at substantially the center of gravity of the club head, which is substantially the geometric center of the blade. For this reason, it is customary in the manufacture of golf clubs to mark the striking face to indicate the center of gravity of the club. This area is commonly called the "sweet spot" or the center portion of the striking face. Moving horizontally along the striking face, the sweet spot is sandwiched between the heel and toe portions of the face.
The marking of the sweet spot offers the golf player a visual sight to focus on to help the player hit the golf ball with the sweet spot of the clubhead. However, such markings are of dubious value because the player cannot well concentrate his attention upon both the center of the ball and the markings of the clubhead.
If the ball is not addressed properly, that is, if the ball hits the heel or toe portions of the striking face, it will hook or slice and travel a distance less than its maximum potential. Since, the object of golf is to reach the hole in the minimum number of shots, such a `mis-hit` would be disadvantageous to the player.
The present invention seeks to solve these problems by providing a "sound and feel" mechanism that is superior to a visual aid mechanism in helping the golfer to properly address the ball. In particular, the present invention modifies the composition of the striking face of the clubhead so that it comprises at least two portions or zones having different degrees of hardness and produces different sounds when struck against the ball. In another embodiment of the invention, the heel and toe portions are made out of metal, while the center portion or sweet spot is made out of a material that is of a different hardness than the metal on either side of it, like fiber glass for example. Such is the clubhead preferred by professional golfers. A beginner is likely to prefer the center portion to be harder so that mis-hits would not travel far.
Hardness is a "[p]roperty of substances determined by their ability to abrade or indent one another." See CRC Handbook of Chemistry and Physics (65th Ed. 1984-85) at F-84, which is incorporated herein by reference. Hardness of a material may be measured by any commonly recognized scientific scale. Two of the most common scales are the MOH values and the KNOOP values. Id. at F-19 and B-198-202.
The original MOH scale runs from 1 to 10 where the higher numbers correspond to the harder materials. For example, Talc, which is very soft, has a MOH value of 1, while diamond, which is universally known as very hard, has a 10 rating on the MOH scale. The following table contains the MOH values for some representative materials:
______________________________________ HARDNESS OF MATERIALS MOH VALUE (Original Scale) ______________________________________ Graphite 0.5-1 Talc 1 Lead 1.5 Tin 1.5-1.8 Aluminum 2-2.9 Copper 2.5-3 Ross' Metal 2.5-3 Wood's Metal 3 Brass 3-4 Bell-Metal 4 Glass 4.5-6.5 Steel 5-8.5 Carbon 10 Diamond 10 ______________________________________
It is apparent from the table that different kinds of metal have different MOH values. Thus, the invention also contemplates an all-metal club using at least two different kinds of metal, or alloys thereof.